Establishing trust-based relationships is a prerequisite for the provision of social work services. Unlike the contractual form of trust prevalent in Western societies, renqing plays a crucial role in the process of building trust within the differential mode of association that characterizes Chinese society. Drawing on in-depth interviews with twenty-six social workers, this study examines how renqing, often regarded as an interfering factor in Western social work, functions as an important resource in China to facilitate trust-building between social workers and clients. The findings identify three core strategies. First, material renqing employs small gifts to reduce clients’ wariness toward strangers and to establish initial trust-based relationships. Second, emotional renqing, through sustained attention and presence at critical moments, deepens trusting relationship from a superficial level to a more substantive one. Third, the renqing norms—such as reciprocity, the preservation of face, and the remembrance of relational obligations—serve to sustain the ongoing operation of trust-based relationships. On this basis, the study examines the theoretical contributions of renqing to trust-building in social work, and rethinks differences in professional boundaries between Chinese and Western social work.